[tip: x86/entry] x86/entry, mce: Disallow #DB during #MC

tip-bot2 for Peter Zijlstra
2020-05-30T09:57:46Z

The following commit has been merged into the x86/entry branch of tip:

Commit-ID: ff98610a03285516b578821549973f969118d6a3
Gitweb: https://git.kernel.org/tip/ff98610a03285516b578821549973f969118d6a3
Author: Peter Zijlstra <peterz@infradead.org>
AuthorDate: Fri, 29 May 2020 23:27:35 +02:00
Committer: Thomas Gleixner <tglx@linutronix.de>
CommitterDate: Sat, 30 May 2020 10:00:08 +02:00

x86/entry, mce: Disallow #DB during #MC

#MC is fragile as heck, don't tempt fate.

Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lkml.kernel.org/r/20200529213321.131187767@infradead.org

---
arch/x86/kernel/cpu/mce/core.c | 12 ++++++++++++
1 file changed, 12 insertions(+)

diff --git a/arch/x86/kernel/cpu/mce/core.c b/arch/x86/kernel/cpu/mce/core.c
index 068e6ca..be49926 100644
--- a/arch/x86/kernel/cpu/mce/core.c
+++ b/arch/x86/kernel/cpu/mce/core.c
@@ -1943,22 +1943,34 @@ static __always_inline void exc_machine_check_user(struct pt_regs *regs)
/* MCE hit kernel mode */
DEFINE_IDTENTRY_MCE(exc_machine_check)
{
+ unsigned long dr7;
+
+ dr7 = local_db_save();
exc_machine_check_kernel(regs);
+ local_db_restore(dr7);
}

/* The user mode variant. */
DEFINE_IDTENTRY_MCE_USER(exc_machine_check)
{
+ unsigned long dr7;
+
+ dr7 = local_db_save();
exc_machine_check_user(regs);
+ local_db_restore(dr7);
}
#else
/* 32bit unified entry point */
DEFINE_IDTENTRY_MCE(exc_machine_check)
{
+ unsigned long dr7;
+
+ dr7 = local_db_save();
if (user_mode(regs))
exc_machine_check_user(regs);
else
exc_machine_check_kernel(regs);
+ local_db_restore(dr7);
}
#endif